The invention relates to an efficient fabrication process and related apparatus for processing lithium anodes for electrochemical cells, such as medium-rate medical grade primary batteries. Typically, during mass production of anodes, the anode material is manually pressed into a cavity in a die having a metallic current collector disposed therein supported by temporary polymer sheet material (e.g., release liner material) interposed to protect the die. During manual anode pressing according to the prior art the lithium material sticks to the removable polymer sheets. Following pressing of the anode the sheets are typically removed and the pressed anode is manually wrapped with a micro-porous separator material and installed in a battery enclosure.
A first polymer insert sheet surrounds the perimeter of the anode and prevents the sides of the lithium anode from contacting the (typically metallic) die during pressing. A commercially available separator sheet is placed on a major side of anode abutting the pressing ram or member. The second sheet optionally remains permanently coupled to the pressed lithium anode. A third sheet (e.g., a so-called parting sheet) approximately 0.002″ thick is interposed between the face of the ram head that pushes the anode current collector—disposed at the bottom of the assembled stack—into the lithium anode.
After pressing, the polypropylene insert sheet is broken free of the sides of the anode using a peeling action and the anode is ejected from the die. The parting sheet is removed and the anode spacer is inspected for damage. The pressed anode is then ready for sealing in a suitable separator material. Using another sheet of commercially available separator material, the anode is then wrapped and placed into a sealing fixture. The separator material can be folded for ease of application and then sealed together around the periphery of the pressed anode to enclose it completely. Thus, the anode subassembly is essentially complete and can be combined with suitable electrolyte and cathode within a sealed enclosure, which for medical devices is typically formed of titanium, stainless steel or the like.
Inherently, the traditional process just described is extremely labor intensive, with discrete variable highly controlled processing requiring the full attention and effort of anode fabrication engineers.
Thus, a need exists in the art to automate the fabrication of anodes to decrease costs, process steps and lot variability with a concomitant increase in manufacturing yield, consistency and quality.